Many boats and other watercraft are driven by one or more inboard or outboard engines or a stern drive system, driving one or more propellers. Each propeller typically has three or four blades, but may have as few as two or as many as five or six. The blades are mounted at an angle, or pitch, relative to a radial axis transverse to the axis of rotation of the propeller shaft. Propellers may be constructed with blades having a fixed pitch. The fixed pitch is typically at an angle that provides maximum efficiency at normal cruising speeds, however fixed pitch propellers typically have reduced efficiency at lower vehicle speeds. As a result, fixed pitch propellers typically have slower acceleration and increased fuel consumption at lower speeds.
One way to improve the efficiency of propellers at most speeds is to provide a propeller with blades having a variable pitch. One example of a variable pitch propeller is described in U.S. Pat. No. 6,896,564, which is hereby incorporated by reference herein in its entirety. Variable pitch propellers allow for increased efficiency at both low and high speeds, but they are typically less sturdy than fixed pitch propellers because each blade must be configured to rotate about a separate pivot axis and various components must be provided within the propeller hub to allow the pitch to be adjusted. Therefore, the entire propeller cannot be constructed as a single rigid component. When a variable pitch propeller is in use, typically at high rotational speeds, the blades are subjected to strong forces that may cause wear or damage to the propeller.
Therefore, there is a need for a variable pitch propeller having a sturdy construction.